Spectral enrichment and wall losses in trombones played at high dynamic levels
Résumé
The characteristic spectral enrichment in the radiated sound of a brass instrument played at high dynamic levels is primarily a result of two closely coupled effects: the nonlinearity at the input to the tube, ie the lip aperture/mouthpiece effect; and the gradual nonlinear distortion of the wave form as it travels along the length of the instrument. In an instrument such as a trombone, which is largely comprised of cylindrical tube, the nonlinear distortion of the wave form can be dramatic, to the point of developing into a shock wave. The higher frequency components of the sound wave suffer more from viscothermal wall losses than do the lower frequency components. These losses act to damp the high frequency components to some extent. Experiments using cylindrical tubes of length and diameter representative of those of a trombone, have been carried out. The results of these experiments are compared with numerical simulations based on weakly nonlinear shock theory in an attempt to better understand the relationship between nonlinear distortion and the effect of the viscothermal losses.
Domaines
Acoustique [physics.class-ph]
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